Friction clutch, for motor vehicle, equipped with a monitored play compensation device

ABSTRACT

A heat engine motor vehicle, having a reaction plate, a friction disc, a pressure plate, a cover, the pressure plate being two half-plates, axially mobile relative to each other, under the action of device compensating play resulting from wear which comprises a pair of complementary ramps circumferentially arranged axially associated respectively with each of the two half-plates one of the ramps being designed to move circumferentially relative to the other ramp in the direction increasing the thickness of the pressure plate, and prevented from moving in the other direction by a one-way mechanism, one of the ramps being arranged at the periphery of an inertial part. A monitoring mechanism, is provided to control the wear compensation device.

The present invention concerns a friction clutch, for a motor vehiclewith a heat engine, and relates more particularly to a clutch equippedwith a device for compensating for the play due principally to the wearof the friction linings, said device working continuously as saidlinings wear.

A conventional friction clutch generally comprises a reaction plate,possibly in two parts for forming a damping flywheel, clampedrotation-wise on a first shaft, usually a drive shaft such as thecrankshaft of the internal combustion engine, and supporting by itsexternal periphery a cover to which at least one pressure plate isattached.

The pressure plate is fixed rotation-wise to the cover and to thereaction plate while being able to move axially under the action ofcontrolled axially-acting elastic means, generally a metal diaphragmresting on the cover, whilst a friction disc, carrying friction liningsat its external periphery, fixed rotation-wise to a shaft, usually adriven shaft such as the input shaft of the gearbox, is inserted betweenthe pressure plate and the reaction plate so as to be gripped betweenthem when the clutch is in the engaged position. The diaphragm controlsthe axial movement of the pressure plate when it is actuated by a clutchrelease bearing.

During the service life of such a clutch, the friction linings and, to alesser extent, the counter-materials, the pressure plate and reactionplate, wear, which causes a variation in the gripping force between thefriction disc, on the one hand, and the pressure and reaction plates, onthe other hand, owing to the changes in the working conditions of thediaphragm.

The clutch travel also varies, as does the force necessary fordisengaging the clutch. By providing such a clutch with a device forcompensating for the play due principally to the wear of the linings,these drawbacks are avoided.

There is known through the document FR 2 426 834 a play compensationdevice in which a first plate, in this case the pressure plate, is madeof two coaxial parts movable axially with respect to one another so thatthe total thickness of the first plate increases as the wear increases.

In this document, the two coaxial parts of the first plate are movableaxially with respect to one another by virtue of a compensation devicewhich comprises ramp means carried in a complementary manner by the twocoaxial parts which are moreover movable rotation-wise with respect toone another in the direction of increasing said total thickness andprevented from turning with respect to one another in the directionopposite to the preceding one by a unidirectional means. The settinginto relative rotational motion of the coaxial parts is controlled by atrigger device sensitive to the wear state and implemented by acircumferentially-acting elastic means coupled between said two coaxialparts.

Such a device effectively makes it possible to continuously compensatefor the play due to the wear of the friction linings.

There has also been proposed, in particular in the document FR-A-2 750467, a clutch of the above kind which is simpler to implement, having asmaller number of pieces.

According to this document, a friction clutch, in particular for a motorvehicle, of the kind comprising a reaction plate intended to be clampedrotation-wise on a drive shaft, a friction disc, carrying frictionlinings at its external periphery, intended to be clamped rotation-wiseon a driven shaft, a pressure plate, a cover fixed on the reactionplate, axially-acting elastic means acting between the cover and thepressure plate, the pressure plate being fixed rotation-wise to thecover while being able to move axially with respect thereto, one of thetwo plates, reaction plate or pressure plate, referred to as the firstplate, consisting of two half-plates, a so-called external half-plateand a so-called internal half-plate, the internal half-plate being theone which faces a friction lining and which is intended to cooperatetherewith, the two half-plates being fixed rotation-wise to the driveshaft but movable axially, with respect to one another, under the actionof a device for compensating for the play due to the wear principally ofthe friction linings, said play compensation device comprising at leastone pair of circumferentially disposed complementary ramps associatedrespectively with each of the two half-plates, one of the ramps,referred to as the support ramp, being fixed rotation-wise to one of thehalf-plates, the other ramp, referred to as the adjustment ramp, beingfixed to the other half-plate and adapted to move circumferentially withrespect to the support ramp, in the direction of increasing the totalthickness of said first plate, referred to as the compensationdirection, and prevented from moving in the other direction by aso-called unidirectional means, said circumferential movement beingcontrolled by a trigger device sensitive to the wear state.

According to this document, the adjustment ramp is formed at theperiphery of an inertia piece, so that the irregular rotation speed ofthe motor vehicle heat engine is utilised in order to make thecomplementary ramps perform their relative circumferential movement inthe play compensation direction. In fact, as is known, the irregularrotation speed results in varying angular accelerations which can reachmore or less two thousand radians per second squared; by virtue of theinertia piece subjected to these angular accelerations, when the clutchis disengaged and, consequently, the two half-plates are no longer underthe axial effort of the axially-acting elastic means, the adjustmentramp turns in the compensation direction with respect to the supportramp, since the unidirectional means prevents it from turning in theother direction. Thus, it is not necessary to provide acircumferentially-acting elastic means between the two so-called coaxialparts and use is made of the irregular rotation speed.

As may also be seen, the operation of the play compensation device isautomatic. Experience has shown that there can be cases where thisautomatic functioning is a drawback since it leads to a compensationoperation not related to wear, a so-called over-compensation operation.

This is the case for example at very low speed, below the idling speed,and in particular when the reaction plate, or flywheel, is a dualdamping flywheel whose own vibration frequency is situated in this rangeof low speeds and produces vibrations leading to the external half-platemoving and compensating for a “play” which does not exist.

Other spurious phenomena can occur at higher speeds, for example abovetwo thousand revolutions per minute.

In order to avoid these drawbacks, there was proposed in the Frenchpatent application filed on 19 May 2000, under number 00 06480, afriction clutch for a motor vehicle with a heat engine, of the kindcomprising a reaction plate intended to be clamped rotation-wise on adrive shaft, a friction disc, carrying friction linings at its externalperiphery, intended to be clamped rotation-wise on a driven shaft, apressure plate, a cover fixed on the reaction plate, axially-actingelastic means acting between the cover and the pressure plate, thepressure plate being fixed rotation-wise to the cover while being ableto move axially with respect thereto, one of the pieces, reaction plateor pressure plate or cover, consisting of two half-pieces, movableaxially, with respect to one another, under the action of a device forcompensating for the play due to wear, said play compensation devicecomprising at least one pair of circumferentially disposed complementaryramps associated axially respectively with each of the two half-pieces,one of the ramps being adapted to move circumferentially with respect tothe other ramp in the direction of increasing the total thickness ofsaid piece, referred to as the compensation direction, and preventedfrom moving in the other direction by a so-called unidirectional means,said circumferential movement being controlled by a trigger devicesensitive to the wear state, one of the ramps being formed at theperiphery of an inertia piece, so that the irregular rotation speed ofthe motor vehicle heat engine is utilised in order to make thecomplementary ramps perform their relative circumferential movement inthe play compensation direction, said clutch comprising control meansadapted to control the play compensation device by enabling, or not, itsoperation.

According to FIGS. 39 and 40 of this document, the unidirectional meansis a split segment and the control means comprise a lever disposedradially overall, the end of which is between the ends of the split ringand which is adapted to expand the split segment.

In the embodiment described and depicted, the internal end of the leveris in a notch in the half-plate which is thus adapted to move this endin one direction or in the other when it is subjected to an accelerationin one direction or in the other, generating locking in the twodirections.

Such a clutch works well; however, in certain cases, the lever, which isnot positively stopped radially, is caused, under the action ofcentrifugal force, to interfere with the control of the playcompensation device.

The aim of the present invention is to remedy these drawbacks.

According to the invention, a friction clutch of the above type ischaracterised by the fact that the lever is mounted able to rotate onsaid piece so that it is held radially with regard to the centrifugalforce.

Advantageously, said piece is one of the two plates, reaction plate orpressure plate, referred to as the first plate, consisting of twohalf-plates, one so-called external half-plate, and one so-calledinternal half-plate, the internal half-plate being the one which faces afriction lining and which is intended to-cooperate therewith, the twohalf-plates being fixed rotation-wise to the drive shaft but movableaxially, with respect to one another, under the action of the playcompensation device, one of the ramps, referred to as the support ramp,being fixed rotation-wise to one of the half-plates, the other ramp,referred to as the adjustment ramp, being adapted to movecircumferentially with respect to the support ramp in the direction ofincreasing the total thickness of said first plate.

Preferably, the support ramp is carried by the internal half-plate.

Advantageously, the adjustment ramp is carried by the externalhalf-plate.

According to a preferred embodiment, the first plate is pressure plate.

Advantageously, the axially-acting elastic means consist of a diaphragm,and the external half-plate is provided with a support bead for thediaphragm.

The adjustment ramp comprises a series of ramps extendingcircumferentially at the end of an annular piece made of cu′ and foldedsheet metal constituting the external half-plate.

Preferably, the lever comprises a so-called active part disposed in linewith the split in the split segment.

Advantageously, the ends of the split segment which define its splithave a radial extension.

Preferably, the radial extension is obtained by tabs added on to theends of the segment.

In a variant, the radial extension is obtained by a looped conformationof the ends of the segment.

Preferably, the segment is made in a single piece.

In a variant, the segment is made from two seamed pieces.

Advantageously, the split segment is held axially.

Preferably, the split segment is held axially by radial barbs, which itcarries internally, received in an external groove or slot.

Preferably, the split segment is acted on elastically circumferentiallyin one direction of rotation.

Advantageously, the rotation means is a spindle; in a variant, therotation means is an articulation.

Advantageously, for axially holding the lever, its active part isreceived in radial slots formed at the ends of the segment.

Other characteristics and advantages of the invention will emergemoreover from the description which follows, by way of example, withreference to the accompanying drawings in which:

FIG. 1 is a partial plan view of a friction clutch according to theinvention;

FIGS. 2 and 3 are sectional views along II—II and III—III of FIG. 1,respectively;

FIG. 4 is an axial sectional view of the external half-plate of theclutch of FIG. 1;

FIG. 5 is a view along arrow V of FIG. 4;

FIG. 6 is a perspective view of the half-plate of FIGS. 4 and 5;

FIG. 7 is a partial view of FIG. 1 on a larger scale;

FIG. 8 is a schematic view illustrating the operation of the controlmeans of the clutch of FIGS. 1 to 7;

FIG. 9 relates to a split ring variant;

FIG. 10 relates to yet another split ring variant;

FIG. 11 is a view analogous to FIG. 7 and shows a variant;

FIG. 12 is a view along arrow XII of FIG. 11.

Referring to FIGS. 1 to 7, it can be seen that the clutch comprises areaction plate 13 intended to be clamped rotation-wise on a drive shaft,here the crankshaft of the a motor vehicle heat engine, a friction disc14 carrying friction linings 15 at its external periphery and intendedto be clamped rotation-wise on a driven shaft.

A cover 11 is fixed on the reaction plate 13 and axially-acting elasticmeans, here a diaphragm 16, act between the cover 11 and a pressureplate 12 fixed rotation-wise to the cover 11 and a pressure plate 12fixed rotation-wise to the cover 11 but able to move axially withrespect thereto, the diaphragm 16 applying, by resting on the cover 11,the pressure plate 12 against the friction disc 14 so that the frictionlinings 15 are gripped between the pressure plate 12 and reaction plate13; as known per se, the diaphragm 16 is mounted so as to be articulatedon the cover 11 by fastenings 21 riveted thereon and rests on the coveraccording to a circumferential reach 20 which it has.

The pressure plate 12 consists of two half-plates; a half-plate 12Areferred to as the external half-plate, and a half-plate 12B, referredto as the internal half-plate, which directly faces the friction disc14; tangential tongues conventionally connect the internal half-plate12B to the cover 11, for connecting, with axial mobility, the pressureplate 12 with the cover 11.

The two half-plates 12A, 12B are fixed rotation-wise to the drive shaftbut movable axially, with respect to one another, under the action of adevice for compensating for play due to wear.

The play compensation device comprises complementary ramps 17, 18disposed circumferentially and associated respectively with each of thetwo half-plates 12A, 12B.

More precisely, the external half-plate 12A is an annular piece housedin line with a step 25 in the internal half-plate 12B; the axial lengthof the annular piece 12A is greater than the axial height of the step 25and its end which faces the cover 11 is shaped as a support bead 19 forthe diaphragm 16.

On its face turned towards the half-plate 12B, the annular piece 12Acarries ramps 18, the axis of which is the axis of the clutch and whichconstitute the adjustment ramp.

By means of its ramps 18, the annular piece 12A constituting theexternal half-plate cooperates with ramps 17, complementary to the ramps18, implemented in the internal half-plate 12B and constituting thesupport ramp.

A split segment 24 surrounds the step 25, being disposed radiallybetween said step 25 and the half-plate 12A. Here, the segment 24 is asingle piece, of overall annular shape.

The direction of the support 17 and adjustment 18 ramps is such that,when the half-plate 12A is subjected to an acceleration in onedirection, the adjustment ramp 18 moves rotation-wise with respect tothe support ramp 17 and the half-plate 12A and, during this movement,moves forward axially with respect to the internal half-plate 12B in thedirection of the cover 11, said direction having been chosenaccordingly; thus, the irregular rotation speed of the heat engine issufficient to make the external half-plate 12A come out axially withrespect to the step 25 if, of course, nothing opposes this coming out,as explained below.

The play compensation device also comprises a trigger device consistingof at least one radially expanding elastic split pin 22 introduced intoa passage 28 through which it passes formed in a radial end lug 29 ofthe internal half-plate 12B; the diameter of the passage 28 is less thanthe external diameter of the pin 22 in the free state so that said pinis mounted with friction in the passage 28 and immobilised axially withrespect to the internal half-plate 12B; this immobilisation friction isprovided with a value such that it can be overcome by the axial effortdue to the diaphragm 16 and it cannot be overcome by the return effortto which the pressure plate 12 is subjected, a return effort such asthat generally coming from the tangential tongues coupling rotation-wisesaid pressure plate 12, here the half-plate 12B, and the cover 11.

Advantageously, three pins such as the pin 22 are provided, introducedinto three passages 28 formed in three lugs 29 of the internalhalf-plate 12B.

The operation of the play compensation device according to the inventionis as follows.

FIGS. 2 and 3 depict the engaged clutch, the friction linings 15 beingnew and gripped between the pressure plate 12 and the reaction plate 13.

In this position, one end of the pins 22 is abutting on the internalface of the reaction plate 13, and the external half-plate 12A is in thein position, axially with respect to the step 25 of the internalhalf-plate 12B.

When the clutch is disengaged, the diaphragm 16 has changed to its endof disengagement travel position; the support bead 19 is no longer incontact with the diaphragm 16; the other end of the pin 22 is in contactwith the cover 11, here the internal face of the radial lug emergingfrom the cover 11; thus, the pin 22 is mounted between this internalface and that of the reaction plate 13 with an axial play 26 whichillustrates the axial travel of the pressure plate 12 duringdisengagement of the clutch.

When there is wear, in particular of the friction linings 15, thepressure plate 12 gets closer to the reaction plate 13, the clutch beingengaged; during this movement, the pin 22 being held axially by itsabutment on the reaction plate 13, the lug 29 of the internal half-plate12B slides over the pin 22 as a result of the axial effort of thediaphragm 16.

At disengaging of the clutch after wear, first the pin 22 has come intoabutment on the cover 11, then the diaphragm has continued its traveland has lifted off the support bead 19; the internal half-plate 12Bhaving drawn back only by an amount equal to the play 26, the shoulder19A of the support bead 19 is at a distance from the cover limit stop11A corresponding to the wear measured axially; subsequently, theexternal half-plate 12A, which is no longer subject to the action of thediaphragm, is free to move in the direction of the diaphragm 16, byvirtue of the accelerations to which it is subjected as a result of theirregular rotation speed of the engine, as explained above; the externalhalf-plate 12A continues to come out until the shoulder 19A of thesupport bead 19 comes into abutment on the cover limit stop 11A: thus,the play due to wear has been compensated for.

When the play due to wear has been compensated for, and the clutch isonce again engaged, the working position of the diaphragm 16 isidentical to that which it had at the beginning, in the new state.

In the embodiment depicted in FIG. 1, the control means comprise a lever30 mounted able to rotate about a rotation means carried here by theinternal half-plate 12B; in the embodiment depicted, the rotation meansis a spindle 31 provided, on the one hand, with a head 32 axiallyholding said lever 30 and, on the other hand, a tail 33 by which it issecured to said half-plate 12B, for example by riveting

The part of the lever 30 which extends radially externally beyond thespindle 31 is disposed in line with the split in the split segment 24;in order that this part, referred to as the active part 32 of the lever30, can be caused to expand said segment 24, under certain conditions,the ends of the split segment 24, which define its split, have a notableradial extension, much greater than the radial thickness of theremainder of the body of the segment 24; here, this radial extension isobtained by tabs 33, 34 added on to the ends of the segment 24, forexample by welding or overmoulding.

The tabs 33, 34 are disposed in an indentation 23 in the internalhalf-plate 12B.

At rest, the lever 30 is pushed by the spring 35 into the position shownin FIG. 8.

During a so-called negative acceleration applied to the plate 12B in theclockwise direction, namely the direction designated by the arrow F inFIG. 8, the split segment 24 and its tabs 33, 34 tend to be movedrelatively in the opposite direction as a result of their own inertia;during this acceleration, the active part 32 of the lever 30, in contactat 36 on the tab 33 and at 37 on the tab 34, the two points 36 and 37being on different radii, expands by lever effect the split segment 24which is then gripped circumferentially against the half-plate 12A andmakes this fixed to the half-plate 12B, thus preventing anycompensation.

For an acceleration in the other direction, an analogous phenomenonwould be obtained but a dissymmetrical operation is introduced.

In order to do this, a spring 35 is disposed in the indentation 23 andis adapted to act on the segment 24 by means of one of the tabs, herethe tab 33, in one direction of rotation, here the anticlockwisedirection.

Thus, for an acceleration according to F, the segment 24 is easilyexpanded and the adjustment ramps 18 are immobilized with respect to thepressure plate 12. The same applies for an acceleration in the otherdirection if it is insufficient to overcome the load of the spring 35.

For an acceleration in the direction opposite to F sufficient toovercome the load of the spring 35, the segment 24 closes up and theadjustment ramps 18 are free: a compensation operation is possible.

Of course, for an acceleration much greater than the load of the spring35, the operation described initially applies, that is to say the splitsegment 24 is expanded and the adjustment ramps 18 are locked relativeto the pressure plate 12.

Thus, by virtue of the spring 35, an oscillation of the lever 30 isavoided as it were between its two positions of locking of the ramps 18by the expansion of the split segment 24.

By suitably calibrating the spring 35, it can be arranged so that, inthe range of ordinary accelerations, the split segment 24 is justslackened, that is to say not expanded, but no more.

By virtue of the spring 35, an over-compensation is avoided for exampleduring the starting of an engine equipped with a dual damping flywheel,which, as is known, for a speed below the idling speed, is subject toresonance phenomena leading to high accelerations.

The calibration of the spring 35 must of course take into account thegearing down effect due to the driving of the split segment 24 by theactive part 32 of the lever 30, while said active part moves apart theedges of the split in the segment 24; this gearing down effect leads toa small expansion of the segment 24, in view of its circumferentialmovement, and therefore to a large effort.

In the example which has just been described, the ends of the segment 24which edge its split have a sufficient radial height obtained by addingon tabs 33, 34 for cooperation with the active part 32 of the lever 30.

This sufficient height can be obtained otherwise, for example by shapingin an appropriate manner the ends of the segment itself.

One example is shown in FIG. 9; here, the ends of a segment 124 havebeen folded back to form loops 133, 134 having parallel straight parts135, 136 defining the split in the split segment 124.

In the embodiment depicted, the split segment 124 carries internallyradial barbs 137, here four barbs 137, intended to be received in anexternal groove or slot in the half-plate 12B with a view to its beingheld axially.

The segment shown in FIG. 10 is similar to the segment of FIG. 9 exceptthat here it is made of two parts 131, seamed at 138.

FIGS. 11 and 12 show a variant of the control means in the form of alever.

Here, the bottom of the indentation 23 communicates by a radial channel38 with an opposite indentation 37, the bottom of which constitutes aseat for a tail 231 of a lever 230, the active part 232 of which,emerging from the tail 231, is here of parallelepipedal shape and passesthrough the radial channel 38; advantageously, the tail 231 cooperateswith said seat according to a cylindrical or spherical reach, said seatbeing able to have a shape complementary to that of this reach. Forretaining it axially, the active part 232 of the lever 230 is receivedin slots 235, 236 formed at the end of the parts 233, 234 of the segment224.

1. Friction clutch for a motor vehicle with a heat engine, comprising a reaction plate (13) intended to be clamped rotation-wise on a drive shaft, a friction disc (14), carrying friction linings (15) at its external periphery, intended to be clamped rotation-wise on a driven shaft, a pressure plate (12), a cover (11) fixed on the reaction plate (13), axially-acting elastic means (16) acting between the cover (11) and the pressure plate (12), the pressure plate (12) being fixed rotation-wise to the cover (11) while being able to move axially with respect thereto, one of the reaction plate (13) and pressure plate (12) and cover (11), including two half-pieces, movable axially, with respect to one another, under the action of a play compensation device for compensating for the play due to wear, said play compensation device comprising at least one pair of circumferentially disposed complementary ramps (17, 18) associated axially respectively with each of the two half-pieces (12A, 12B), one of the ramps (17) being adapted to move circumferentially with respect to the other ramp (18) in a compensation direction of increasing the total thickness of said piece, and prevented from moving in the other direction by a unidirectional means (24, 124, 224), said circumferential movement being controlled by a trigger device (22) sensitive to the wear state, one of the ramps (18) being formed at the periphery of an inertia piece (12A), so that the irregular rotation speed of the motor vehicle heat engine is utilized in order to make the complementary ramps perform their relative circumferential movement in the play compensation direction, said clutch comprising control means adapted to control the play compensation device by selectively enabling its operation, said unidirectional means (24, 124, 224) being a split segment (24, 124, 224) fixed rotation-wise to said piece (12) and the control means, sensitive to acceleration, comprising a lever (30, 230) disposed radially overall, the end of which is between the ends of the split ring (24, 124, 224) and which is adapted to expand the split segment (24, 124, 224) wherein the lever (30, 230) is mounted able to rotate on said piece (12) so that it is held radially with regard to the centrifugal force.
 2. Clutch according to claim 1, wherein said piece is one of the reaction plate (13) and pressure plate (12), referred to as the first plate, consisting of two half-plates, an external half-plate (12A) and an internal half-plate (12B), the internal half-plate (12B) being the one which faces a friction lining and which is intended to cooperate therewith, the two half-plates (12A, 12B) being fixed rotation-wise to the drive shaft but movable axially, with respect to one another, under the action of the play compensation device, one of the ramps (17), referred to as the support ramp, being fixed rotation-wise to one (12B) of the half plates, the other ramp (18), referred to as the adjustment ramp, being adapted to move circumferentially with respect to the support ramp (17) in the direction of increasing the total thickness of said first plate.
 3. Clutch according to claim 2, wherein the support ramp (17) is carried by the internal half-plate (12B).
 4. Clutch according to claim 3, wherein the axially-acting elastic means (16) comprises a diaphragm, and wherein the external half-plate (12A) is provided with a support bead (19) for the diaphragm.
 5. Clutch according to claim 2, wherein the first plate is the pressure plate (12).
 6. Clutch according claim 2, wherein the adjustment ramp (18) is carried by the external half-plate (12A).
 7. Clutch according to claim 2, wherein the adjustment ramp (18) comprises a series of ramps extending circumferentially at the end of an annular piece (12A) made of cut and folded sheet metal constituting the external half-plate.
 8. Clutch according to claim 1, wherein the lever (30, 230) comprises an active part (32, 232) disposed in line with the split in the split segment (124, 224).
 9. Clutch according to claim 1, wherein the ends (33, 133, 233–34, 134, 234) of the split segment (24, 124, 224) which define its split have a radial extension.
 10. Clutch according to claim 9, wherein the radial extension is obtained by tabs (33, 233–34, 234) added on to the ends of the segment (24, 224).
 11. Clutch according to claim 9, wherein the radial extension is obtained by a looped conformation (133, 134) of the ends of the segment (124).
 12. Clutch according to claim 9, wherein the segment (124) is made in a single piece.
 13. Clutch according to claim 9, wherein the segment (124) is made from two seamed (138) pieces (131, 132).
 14. Clutch according to claim 9, wherein the split segment (124) is held axially.
 15. Clutch according to claim 14, wherein the split segment (124) is held axially by radial barbs (137), which it carries internally, received in an external groove or slot.
 16. Clutch according to claim 1, wherein the split segment (24, 124, 224) is acted on elastically (35) circumferentially in one direction of rotation.
 17. Clutch according to claim 1, wherein the rotation means is a spindle (31).
 18. Clutch according to claim 1, wherein the rotation means is an articulation (231).
 19. Clutch according to claim 18, wherein, for axially holding the lever (230), an active part (232) is received in radial slots (235, 236) formed at the ends of the segment (224). 